I think you need to take the original statement with a grain of salt. However the fundamentals for a street/track car seem sound.

The way I look at it, is with a singe adjustable shock, compression tuning can be affected by the chosen spring rate. Obviously there are limits to this.

 

This question will further confuse you. Because no, it's the opposite.

Higher spring rate requires higher damping to have the same damping effect on the spring.

That's why you need a higher damping in rebound for a higher spring rate. Because rebound is much more of a science than compression is, you're just trying to control the spring in vibration like most dampers do.

Compression in race cars is a weird one because many don't use it in the ways that dampers are normally used in engineering. People use it in a bunch of different ways, particularly as a substitute for spring force. If you're taking away spring and substituting for the change with shocks, then you'll go to higher compression, even though classical vibrations engineering says that you actually need less compression for the same damping because the spring will resonate at a lower frequency. That's because you're using the shock as a spring, not as a damper.

So the answer to the question is that it depends on how you're using your shocks. In some cases you'd want more compression, in some you'd want less, in some you won't touch it. Basically the more compression you have relative to rebound and relative to spring rate, the more chance you'd want to follow the koni advice.

But again rebound is much more clear. There if your car wasn't too bouncy before the spring change, then to keep that behavior you would up rebound with higher spring rates and vice versa.

This is why rebound only adjustable shocks are far more common than compression only.

Oh and also...dampening means "to make wet" . Damping is the word you're looking for.

 

Yes, I am confused.

Also, who wrote dampening??

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Doh!!!

 

Apparently you decided to mix and match?

Sorry for confusing you further. I rewrote it a couple times then decided I can't make it any clearer. Not because it's clear as I wrote it but just because it's complicated. Shocks are hard.

 

OK look at it this way...let's break it down into the basics.

So imagine you drive down a perfectly smooth road and hit a single bump, then it's perfectly smooth again.

1) If there are no shocks and no friction damping the springs, the car will just keep bouncing forever after the bump because it's got springs with no damping so they bounce back and forth.

2) If the shocks are underdamped, the car will keep bouncing after hitting the bump for at least one full cycle, the more underdamped it is the more bounces it will take before it stops bouncing.

3) Critically damped means it bounces just once exactly.

4) Overdamped means the wheel just slowly returns to full ride height with no overshoot.

That's damping. It's the main job of the shock, to make sure you don't bounce too much.

I won't go through the math but basically if you raise the spring rate then to be exactly the same ratio of under/over damped you have to raise the damping. If you don't then you will be more underdamped than before. And vice versa - lower the spring rate and you'll be more damped if you don't change the shocks to match.

So say your car is not bouncy at all and is the perfect amount of damping. Then you install much stiffer springs without changing shocks. Your car will bounce around a lot more than optimal. If this happened and you had compression adjustment only, you would turn it up to make the car not bouncy again.

So for the purposes of damping, more spring rate = more damping to keep everything the same.

So this is one variable.


Then on the other side, there's something completely separate, which is the fact that you can turn up your dampers and make it actually resist body movement for handling tuning purposes. This is a different thing. And it shows, because here it's the complete opposite for compression. Here if the car is perfect where it's stiff but just barely not skipping over bumps, and part of that is you have a lot of compression valving, then you raise the spring rate.....then it may be too stiff. To fix that one route would be to lower the compression damping and raise the rebound. That way the car doesn't bounce too much because the rebound takes care of the damping you lost in compression, while taking out compression makes it more compliant.

So two separate things. Damping and effective spring rate. They work in opposite directions for what you want with higher spring rate.

If you have something like a koni yellow which has very little compression, then you don't have to worry about compression adjustment when changing springs because the compression is so small relative to everything else anyway. But if you have something like a moton at full stiff then you have to worry more about the effective spring rate part of things.

Anyway that's lots of words but hopefully it makes more sense now?

 

good post

 

Nice!

Ok makes sense. For body control it seems rebound is more critical. For controlling the unsprung mass, compression is more critical.

 

I find this statement much less helpful.

As has been explained by others, the stiffer the spring, the more damping you need, not less. That may bias more to the rebound side of things, but not always. Anything running with aero on track or without it but on rough surfaces (so all you roadgoers that aren't on butter smooth tracks) will tend to want more compression damping as well with stiffer springs, even if the ratio between it and rebound changes.
Aero settings are very relevent for fast road cars because both deal with heave effects that normal race cars don't encounter.

 

Can you edit your with/with statement for clarity?

Do you mean to say that even on a rough track, with aero, you need more compression with stiffer springs? Sounds like a recipe for a rough ride and a hard track to run aero at.

 

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